<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>模板标题记得要改！！！！！！！！！！</title>
    <link href="bootstrap-4.6.1-dist/css/bootstrap.css"
          rel="stylesheet" type="text/css">
    <style>
        .dropdown{
            margin-bottom: -20px;
        }
        .dropdown:hover{
            margin: 0px;
        }
        .show{
            /*display: block;*/
            overflow: hidden;
            visibility: hidden;
            max-height: 0px;
            transform: scaleY(0);
        }
        .dropdown:hover .show{
            visibility: visible;
            overflow: hidden;
            transition: transform 0.2s;
            max-height: 999999px;
            transform: scaleY(1);
        }
        .userPortrait {
            width: 40px;
            height: 40px;
            border: 1px solid red;
            border-radius: 50%;
            overflow: hidden;
            margin: 0 auto;
            /*margin-top: 100px;*/
        }
        .userPortrait img {
            display: block;
            width: 100%;
            height:100%;
            border: 1px solid green;
        }
    </style>
</head>
<body>

<!--眉头-->
<nav class="navbar navbar-expand-lg navbar-dark bg-primary">
    <a class="navbar-brand col-1 text-center" href="index.html">爱思教育</a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarText" aria-controls="navbarText" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse">
        <ul class="navbar-nav">
            <li class="nav-item">
                <a class="nav-link active" href="#">菜单</a>
            </li>
            <li class="nav-item active">
                <a class="nav-link" href="#">菜单</a>
            </li>
            <li class="nav-item active dropdown">
                <a class="nav-link dropdown-toggle" href="#" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                    下拉菜单
                </a>
                <div class="dropdown-menu show" aria-labelledby="navbarDropdownMenuLink">
                    <a class="dropdown-item" href="#">下拉项1</a>
                    <a class="dropdown-item" href="#">下拉项2</a>
                    <a class="dropdown-item" href="#">下拉项3</a>
                </div>
            </li>
            <li class="nav-item active dropdown">
                <a class="nav-link dropdown-toggle" href="#" data-toggle="dropdown" aria-haspopup="true" aria-expanded="true">
                    下拉菜单
                </a>
                <div class="dropdown-menu show" aria-labelledby="navbarDropdownMenuLink">
                    <a class="dropdown-item" href="#">下拉项1</a>
                    <a class="dropdown-item" href="#">下拉项2</a>
                    <a class="dropdown-item" href="#">下拉项3</a>
                </div>
            </li>
        </ul>
    </div>
    <div class="userPortrait active dropdown">
        <a href="userInformation.html"><img src="img/defaultPortrait.jpg" alt=""></a>
    </div>
</nav>

<!--中间-->
<div class="row">
    <!--侧边栏-->
    <ul class="navbar-nav bg-light text-center col-md-2">
        <li class="nav-item">
            <a class="nav-link btn btn-light" href="#">侧边栏是做页内导航的</a>
<!--            <div class="dropdown-menu text-center show"></div>-->
        </li>
        <li class="nav-item">
            <a class="nav-link btn btn-light" href="#">导航到本菜单内</a>
<!--            <div class="dropdown-menu text-center show"></div>-->
        </li>
        <li class="nav-item dropdown">
            <a class="nav-link btn btn-light dropdown-toggle" href="#">或者某个下拉菜单内</a>
            <div class="dropdown-menu text-center show">
                <a class="dropdown-item" href="#">子选项</a>
                <a class="dropdown-item" href="#">子选项</a>
                <a class="dropdown-item" href="#">子选项</a>
            </div>
        </li>
        <li class="nav-item dropdown">
            <a class="nav-link btn btn-light dropdown-toggle" href="#">不要导航到其它列的菜单</a>
            <div class="dropdown-menu text-center show">
                <a class="dropdown-item" href="#">子选项</a>
                <a class="dropdown-item" href="#">子选项</a>
                <a class="dropdown-item" href="#">子选项</a>
            </div>
        </li>
    </ul>

    <!--主页面-->
    <div class="main col-10">
        在这里写代码
    </div>
</div>

<!--页脚-->
<div class="footer bg-primary fixed-bottom text-center">
    <p class="text-white">版权所有© Copyright 1999-2021 爱思软件股份有限公司　　中国·青岛黄岛区嘉陵江路777号 西区公寓2号   版本V-0.0.1</p>
</div>

</body>
</html>
